1. Field of the Invention
This invention relates to an automatic charge receipt system for automatically collecting a utilization (i.e., toll) charge pertaining to vehicle/use information and utilization charge information as communicated between a vehicle running on a utilization charge road (i.e., toll road) and a road-side device (toll booth) installed in a road-side system, and to a vehicle-mounted device to be installed on the vehicle for effecting such communication.
2. Description of Related Art
In recent years, there has been studied an automatic charge receipt system for automatically collecting a charge (i.e., toll) from a vehicle running on a charged road. This technology is operated such that a road-to-vehicle communication is carried out using an electromagnetic wave communication between a vehicle-mounted device installed on the vehicle and a road-side device installed in a road-side system (e.g., toll both) so as to exchange information about charge payment so as to determine/settle a utilization charge. Examples of automatic charge collection systems include the "Electric Toll Collection" system in Japan, "Auto Fee Collection" system in Europe, and "Fastoll" system in the United States.
As a practical settlement met hod, it has been proposed that information on a current expendable balance (e.g., an electronic cash balance on account) is written in advance in the vehicle-mounted device in place of cash, for example, via pre-paid toll cards. A request for information on a utilizing charge is sent from the road-side device to the vehicle-mounted device as a charge is incurred (e.g., as the vehicle passes the toll booth), and then a utilization charge is subtracted within the vehicle-mounted device from the current expendable balance.
In addition, in order to determine an appropriate charge in reference to a travel route which the vehicle uses (e.g., point of entrance of the toll road) and information about the type of vehicle (e.g., truck/car, number of axles, private/commercial status, etc.), it has been considered to adapt the vehicle-mounted device to also transmit information about the route or the type of vehicle to the road-side device.
In the aforesaid automatic charge receipt system, information concerning money is exchanged and settled using communication transmission, and accordingly, it is necessary to provide a countermeasure (i.e., to protect an integrity and security) for preventing any irregular utilization or theft via interception and/or modification of the content of communication. As one countermeasure, there can be considered an encrypting/decrypting of the content of communication.
In the case that a communication performed between the road-side device and the vehicle-mounted device is encrypted, the road-side device has to be able to decrypt the encrypted communication transmitted by a large number of random vehicle-mounted devices. Due to this fact, algorithms for encrypting/decrypting must be at least unified in an entire automatic receipt system. In addition, there may be applied a method for installing a different encrypting/decrypting key within every vehicle-mounted device or a method for installing one common key over an entire automatic charge receipt system. With respect to such keys, it is necessary to securely distribute and monitor the encrypting/decrypting keys in such a way that they may not be leaked out and used to thwart the charge receipt system.
As one complicating factor, designing and manufacturing of the vehicle-mounted device are not always necessarily carried out by a centralized manager for an automatic charge receipt system, because the designing and manufacturing of various kinds of vehicle-mounted devices in compliance with various kinds of vehicles can be more effectively and efficiently carried out by a vehicle manufacturer rather than the manager. In such a case where numerous vehicle manufacturers are manufacturing/installing vehicle-mounted devices, a number of persons having access to an encrypting/decrypting algorithm or encrypting/decrypting keys is increased and it becomes hard to monitor them in such a way that they may not be leaked out. In addition, from the standpoint of the vehicle manufacturer, it is not essential for such manufacturer to handle an encrypting/decrypting algorithm or keys, and so it is preferable to enable vehicle-mounted devices to be manufactured/installed while encrypting/decrypting algorithms and keys remain hidden.